Question

The shelf life of a battery produced by one major company is known to be Normally distributed, with a mean life of 7.3 years and a standard deviation of 1.4 years.

What value of shelf life do 16% of the battery shelf lives fall above? Round your answer to one decimal place.

Answer 1

Let define a random variable X that represent shelf life of me battery.

The random variable X is normally distributed with mean 7.3 years and standard deviation 1.4 years.

i.e, X~N(7.3,1.4)

Let m be the value of shelf life do 16% of the battery shelf lives fall above it.

i.e, P(X>m)=0.16

From the standard normal table we get,

[ round to 1-decimal place]

The value is 8.7